A high-sensitivity magnetic field measurement device and method

Abstract

The present invention discloses a high-sensitivity magnetic field measuring device and method. The magnetic field measuring device comprises a laser light source, a Fabry-Perot cavity, a magnetostrictive material rod, a photodetector and a computing device. When measuring the magnetic field, the entire magnetic field measuring device is placed in a magnetic field environment to be measured. The laser emitted by the laser light source reaches the photodetector after passing through the Fabry-Perot cavity. The light output end of the Fabry-Perot cavity is fixed to the magnetostrictive material rod. The computing device is connected to the photodetector and is used to form a transmission spectrum according to the optical signal detected by the photodetector, and then calculate the offset of the resonant frequency of the Fabry-Perot cavity compared to the preset reference resonant frequency according to the transmission spectrum, and then calculate the magnetic field size of the magnetic field environment according to the offset. The device of the present invention is simple, low in cost and high in sensitivity.

Description

Technical Field

[0001] The present invention relates to magnetic field measurement technology, and in particular to a high-sensitivity magnetic field measurement device and method. Background Art

[0002] Magnetic field is one of the most basic vector fields in nature. With the development of social science and technology, there is an increasing need to make more accurate measurements of magnetic fields. At present, the measurement research of magnetic fields can be divided into three categories: weak magnetic field, strong magnetic field, and ultra-strong magnetic field. Among them, the measurement of weak magnetic field has received extensive attention because of its great significance in military defense, resource exploration, biomedicine, and aerospace.

[0003] At present, the main methods for measuring weak magnetic fields include superconducting quantum interference magnetometers, atomic magnetometers, diamond NV color center magnetometers, etc. However, the structures of these devices are relatively complex, and the requirements for experimental environment and experimental conditions are also very stringent. Therefore, how to manufacture a magnetic measurement device with lower cost and better flexibility has become one of the main research directions of domestic and foreign scholars.

[0004] Previously, some researchers proposed a magnetic measurement device based on magnetostrictive materials, see [Xinxing Feng, Yi Jiang, and Han Zhang. A mechanical amplifier based high-finesse fiber-optic Fabry-Perot interferometric sensor for the measurement of static magnetic field, Meas. Sci. Technol. 12 (2021): 32]. This device combines magnetostrictive materials with Fabry-Perot fiber cavities. By changing the magnetostrictive materials, the resonance spectrum of the Fabry-Perot fiber cavities is shifted, and the magnetic field is detected. However, since the magnetostrictive materials are placed in the cavity, the ratio of the change in cavity length to the original cavity length is small, and the sensitivity is limited. Therefore, it is very important to improve the sensitivity of the magnetic measurement device while ensuring its advantages such as simple structure and low cost. Summary of the invention

[0005] Purpose of the invention: To solve the problems existing in the prior art, the present invention provides a high-sensitivity magnetic field measurement device and method.

[0006] Technical solution: The high-sensitivity magnetic field measuring device of the present invention is characterized in that it includes a laser light source, a Fabry-Perot cavity, a magnetostrictive material rod, a photodetector and a computing device. When measuring the magnetic field, the entire magnetic field measuring device is placed in the magnetic field environment to be measured, the laser emitted by the laser light source reaches the photodetector after passing through the Fabry-Perot cavity, the light output end of the Fabry-Perot cavity is fixed to the magnetostrictive material rod, the computing device is connected to the photodetector, and is used to form a transmission spectrum according to the light signal detected by the photodetector, and then calculate the offset of the resonant frequency of the Fabry-Perot cavity compared to the preset reference resonant frequency according to the transmission spectrum, and then calculate the magnetic field size of the magnetic field environment according to the offset.

[0007] Furthermore, the computing device comprises:

[0008] A transmission spectrum generating module, used to calculate the transmittance of the optical signal received by the photodetector according to the optical power of the optical signal received by the photodetector, and form a transmission spectrum;

[0009] An offset extraction module, used to obtain the resonance frequency of the Fabry–Perot cavity according to the transmission spectrum, and calculate the offset of the resonance frequency of the Fabry–Perot cavity compared to a preset reference resonance frequency;

[0010] The magnetic field calculation module is used to calculate the magnetic field size of the magnetic field environment according to the offset according to the following formula:

[0011]

[0012] Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

[0013] Furthermore, the preset reference resonant frequency is the resonant frequency of the Fabry–Perot cavity in a zero magnetic environment.

[0014] Furthermore, the Fabry–Perot cavity is specifically a Fabry–Perot optical microcavity, which includes a first plano-concave cavity mirror and a second plano-concave cavity mirror arranged along the light propagation direction, and the magnetostrictive material rod is fixed together with the second plano-concave cavity mirror.

[0015] Furthermore, the Fabry–Perot cavity is specifically a Fabry–Perot fiber cavity, which includes a first fiber end and a second fiber end arranged along the light propagation direction, and the magnetostrictive material rod is fixed to the second fiber end through a plastic block.

[0016] Furthermore, the magnetostrictive material used in the magnetostrictive material rod is terbium-dysprosium-iron alloy or iron-gallium alloy.

[0017] Furthermore, the first plano-concave cavity mirror and the second plano-concave cavity mirror are both coated with a dielectric film corresponding to the laser wavelength emitted by the laser light source.

[0018] The high-sensitivity magnetic field measurement method of the present invention is based on the above-mentioned magnetic field measurement device, and specifically comprises the following steps:

[0019] (1) placing the magnetic field measuring device in a zero magnetic environment, measuring the length of the magnetostrictive material rod and the cavity length of the Fabry–Perot cavity, and calculating the resonant frequency of the Fabry–Perot cavity as a preset reference resonant frequency;

[0020] (2) The magnetic field measuring device is placed in the magnetic field environment to be measured, and a transmission spectrum is formed according to the light signal detected by the photodetector. Then, the offset of the resonant frequency of the Fabry–Perot cavity compared to the preset reference resonant frequency is calculated according to the transmission spectrum, and then the magnetic field size of the magnetic field environment is calculated according to the offset.

[0021] Furthermore, step (2) specifically includes:

[0022] According to the optical power of the optical signal received by the photodetector, the transmittance of the optical signal received by the photodetector is calculated, and a transmission spectrum is formed;

[0023] The resonant frequency of the Fabry–Perot cavity is obtained according to the transmission spectrum, and the offset of the resonant frequency of the Fabry–Perot cavity compared with the preset reference resonant frequency is calculated;

[0024] The magnitude of the magnetic field in the magnetic field environment is calculated according to the following formula based on the offset:

[0025]

[0026] Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

[0027] The ratio of the change in cavity length of the Fabry–Perot cavity to the original cavity length in a zero magnetic environment can approach 1. Compared with the prior art, the present invention has the following beneficial effects: the device of the present invention is simple and low in cost, and compared with the previous magnetic measurement device in which the magnetostrictive material is placed in the cavity, the present invention connects the magnetostrictive material to one end of the optical microcavity, so the ratio of the change in cavity length to the original cavity length (ΔL / LC) can be as large as possible, or even infinitely close to 1, which makes the magnetic measurement device more sensitive. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a structural diagram of an embodiment of a high-sensitivity magnetic field measuring device provided by the present invention;

[0029] Figure 2 It is a structural diagram of another embodiment of the high-sensitivity magnetic field measuring device provided by the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] Embodiment 1

[0032] This embodiment provides a high-sensitivity magnetic field measurement device, such as Figure 1As shown, it includes a laser light source 1, a Fabry-Perot cavity 2, a magnetostrictive material rod 3, a photodetector 4 and a computing device (not shown). When measuring the magnetic field, the entire magnetic field measuring device is placed in the magnetic field environment to be measured. The laser emitted by the laser light source 1 reaches the photodetector 4 after passing through the Fabry-Perot cavity 2. The Fabry-Perot cavity 2 is specifically a Fabry-Perot optical microcavity, including a first plano-concave cavity mirror and a second plano-concave cavity mirror arranged along the light propagation direction, and the first plano-concave cavity mirror and the second plano-concave cavity mirror are both coated with a dielectric film corresponding to the laser wavelength emitted by the laser light source. The magnetostrictive material rod 3 is fixed to the second plano-concave cavity mirror, specifically pasted behind the second plano-concave cavity mirror, and the magnetostrictive material used in the magnetostrictive material rod 3 is terbium-dysprosium-iron alloy (Teflon D, Terfenol-D) or iron-gallium alloy Galfenol). The calculation device is connected to the photodetector 4, and is used to form a transmission spectrum according to the light signal detected by the photodetector, and then calculate the offset of the resonant frequency of the Fabry-Perot cavity compared to the preset reference resonant frequency according to the transmission spectrum, and then calculate the magnetic field size of the magnetic field environment according to the offset. The preset reference resonant frequency is the resonant frequency of the Fabry-Perot cavity in a zero magnetic environment.

[0033] The calculation device includes a transmission spectrum generation module, a transmission spectrum generation module and an offset extraction module. The transmission spectrum generation module is used to calculate the transmittance of the optical signal received by the photodetector according to the optical power of the optical signal received by the photodetector, and form a transmission spectrum, wherein calculating the transmittance by optical power is a prior art, for example, the optical power of the optical signal received by the photodetector is divided by the optical power of the laser emission signal as the transmittance; the offset extraction module is used to obtain the resonant frequency of the Fabry–Perot cavity according to the transmission spectrum, and calculate the offset of the resonant frequency of the Fabry–Perot cavity compared to the preset reference resonant frequency, wherein the transmission spectrum can reflect the resonant frequency of the Fabry–Perot cavity, so the resonant frequency of the Fabry–Perot cavity can be obtained according to the transmission spectrum, and the specific method is a prior art and will not be repeated; the magnetic field calculation module is used to calculate the magnetic field size of the magnetic field environment according to the following formula based on the offset:

[0034]

[0035] Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

[0036] This embodiment also discloses a high-sensitivity magnetic field measurement method, which is based on the above magnetic field measurement device and specifically includes the following steps:

[0037] (1) placing the magnetic field measuring device in a zero magnetic environment, measuring the length of the magnetostrictive material rod and the cavity length of the Fabry–Perot cavity, and calculating the resonant frequency of the Fabry–Perot cavity as a preset reference resonant frequency; wherein the ratio of the cavity length change of the Fabry–Perot cavity in the zero magnetic environment to the original cavity length can approach 1, that is, the cavity length of the Fabry–Perot cavity in the zero magnetic environment should be as small as possible, so that the ratio of the cavity length change caused by the magnetic field change to the original cavity length is as large as possible, thereby improving sensitivity;

[0038] (2) The magnetic field measuring device is placed in the magnetic field environment to be measured, and a transmission spectrum is formed according to the light signal detected by the photodetector. Then, the offset of the resonant frequency of the Fabry–Perot cavity compared to the preset reference resonant frequency is calculated according to the transmission spectrum, and then the magnetic field size of the magnetic field environment is calculated according to the offset.

[0039] This step specifically includes:

[0040] According to the optical power of the optical signal received by the photodetector, the transmittance of the optical signal received by the photodetector is calculated, and a transmission spectrum is formed;

[0041] The resonant frequency of the Fabry–Perot cavity is obtained according to the transmission spectrum, and the offset of the resonant frequency of the Fabry–Perot cavity compared with the preset reference resonant frequency is calculated;

[0042] The magnitude of the magnetic field in the magnetic field environment is calculated according to the following formula based on the offset:

[0043]

[0044] Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

[0045] Embodiment 2

[0046] This embodiment provides another high-sensitivity magnetic field measuring device, such as Figure 2As shown, it includes a laser light source 1, a Fabry-Perot cavity 2, a magnetostrictive material rod 3, a photodetector 4 and a computing device (not shown). When measuring the magnetic field, the entire magnetic field measuring device is placed in the magnetic field environment to be measured. The laser emitted by the laser light source 1 reaches the photodetector 4 after passing through the Fabry-Perot cavity 2. The Fabry-Perot cavity 2 is specifically a Fabry-Perot optical fiber cavity, including a first optical fiber end and a second optical fiber end arranged along the light propagation direction. The magnetostrictive material rod 3 is fixed to the second optical fiber end through a plastic block 5 (for example, a polyester tetrafluoroethylene block). The magnetostrictive material rod 3 is not directly connected to the second optical fiber end, but a plastic block 5 is fixed at the end of the magnetostrictive material rod 3. The plastic block 5 is fixed to the second optical fiber end, and the purpose is to prevent the change in the length of the magnetostrictive material from pulling the optical fiber itself and causing errors. The magnetostrictive material used in the magnetostrictive material rod 3 is terbium dysprosium iron alloy (Teflon D, Terfenol-D) or iron gallium alloy Galfenol). The calculation device is connected to the photodetector 4, and is used to form a transmission spectrum according to the light signal detected by the photodetector, and then calculate the offset of the resonant frequency of the Fabry-Perot cavity compared to the preset reference resonant frequency according to the transmission spectrum, and then calculate the magnetic field size of the magnetic field environment according to the offset. The preset reference resonant frequency is the resonant frequency of the Fabry-Perot cavity in a zero magnetic environment.

[0047] The calculation device includes a transmission spectrum generation module, a transmission spectrum generation module and an offset extraction module. The transmission spectrum generation module is used to calculate the transmittance of the light signal received by the photodetector according to the optical power of the light signal received by the photodetector, and form a transmission spectrum; the offset extraction module is used to obtain the resonant frequency of the Fabry-Perot cavity according to the transmission spectrum, and calculate the offset of the resonant frequency of the Fabry-Perot cavity compared to the preset reference resonant frequency; the magnetic field calculation module is used to calculate the magnetic field size of the magnetic field environment according to the following formula according to the offset:

[0048]

[0049] Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

[0050] This embodiment also discloses a high-sensitivity magnetic field measurement method, which is based on the above magnetic field measurement device and specifically includes the following steps:

[0051] (1) placing the magnetic field measuring device in a zero magnetic environment, measuring the length of the magnetostrictive material rod and the cavity length of the Fabry–Perot cavity, and calculating the resonant frequency of the Fabry–Perot cavity as a preset reference resonant frequency; wherein the ratio of the cavity length change of the Fabry–Perot cavity in the zero magnetic environment to the original cavity length can approach 1, that is, the cavity length of the Fabry–Perot cavity in the zero magnetic environment should be as small as possible, so that the ratio of the cavity length change caused by the magnetic field change to the original cavity length is as large as possible, thereby improving sensitivity;

[0052] (2) The magnetic field measuring device is placed in the magnetic field environment to be measured, and a transmission spectrum is formed according to the light signal detected by the photodetector. Then, the offset of the resonant frequency of the Fabry–Perot cavity compared to the preset reference resonant frequency is calculated according to the transmission spectrum, and then the magnetic field size of the magnetic field environment is calculated according to the offset.

[0053] This step specifically includes:

[0054] According to the optical power of the optical signal received by the photodetector, the transmittance of the optical signal received by the photodetector is calculated, and a transmission spectrum is formed;

[0055] The resonant frequency of the Fabry–Perot cavity is obtained according to the transmission spectrum, and the offset of the resonant frequency of the Fabry–Perot cavity compared with the preset reference resonant frequency is calculated;

[0056] The magnitude of the magnetic field in the magnetic field environment is calculated according to the following formula based on the offset:

[0057]

[0058] Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

[0059] It is worth noting that in the embodiment of the above-mentioned determination device, the various units and modules included are only divided according to functional logic, but are not limited to the above-mentioned division, as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention.

[0060] The embodiments described above are only illustrative, wherein the modules described as separate components may or may not be physically separated, and the components displayed as modules may or may not be physical modules, i.e., they may be located in one place, or they may be distributed on multiple network modules. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, or of course, it can be implemented only by hardware, as long as the function or effect can be achieved.

[0061] The terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order. The reference to "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

Claims

1. A high-sensitivity magnetic field measuring device, characterized in that: The device comprises a laser light source, a Fabry-Perot cavity, a magnetostrictive material rod, a photodetector and a calculation device. When measuring a magnetic field, the entire magnetic field measurement device is placed in a magnetic field environment to be measured. The laser emitted by the laser light source reaches the photodetector after passing through the Fabry-Perot cavity. The light output end of the Fabry-Perot cavity is fixed to the magnetostrictive material rod. The calculation device is connected to the photodetector and is used to form a transmission spectrum according to a light signal detected by the photodetector, and then calculate the offset of the resonant frequency of the Fabry-Perot cavity compared to a preset reference resonant frequency according to the transmission spectrum, and then calculate the magnetic field size of the magnetic field environment according to the offset. Wherein, the computing device comprises: A transmission spectrum generating module, used to calculate the transmittance of the optical signal received by the photodetector according to the optical power of the optical signal received by the photodetector, and form a transmission spectrum; An offset extraction module, used to obtain the resonance frequency of the Fabry–Perot cavity according to the transmission spectrum, and calculate the offset of the resonance frequency of the Fabry–Perot cavity compared to a preset reference resonance frequency; The magnetic field calculation module is used to calculate the magnetic field size of the magnetic field environment according to the offset according to the following formula: Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

2. The high-sensitivity magnetic field measuring device according to claim 1, characterized in that: The preset reference resonant frequency is the resonant frequency of the Fabry–Perot cavity in a zero magnetic environment.

3. The high-sensitivity magnetic field measuring device according to claim 1, characterized in that: The Fabry–Perot cavity is specifically a Fabry–Perot optical microcavity, which comprises a first plano-concave cavity mirror and a second plano-concave cavity mirror arranged along the light propagation direction, and the magnetostrictive material rod is fixed together with the second plano-concave cavity mirror.

4. The high-sensitivity magnetic field measuring device according to claim 1, characterized in that: The Fabry–Perot cavity is specifically a Fabry–Perot fiber cavity, which includes a first fiber end and a second fiber end arranged along the light propagation direction, and the magnetostrictive material rod is fixed to the second fiber end through a plastic block.

5. The high-sensitivity magnetic field measuring device according to claim 1, characterized in that: The magnetostrictive material used in the magnetostrictive material rod is terbium-dysprosium-iron alloy or iron-gallium alloy.

6. The high-sensitivity magnetic field measuring device according to claim 3, characterized in that: The first plano-concave cavity mirror and the second plano-concave cavity mirror are both coated with a dielectric film corresponding to the laser wavelength emitted by the laser light source.

7. A high-sensitivity magnetic field measurement method, characterized in that: The method is based on the magnetic field measuring device according to claim 1, and specifically comprises the following steps: (1) placing the magnetic field measuring device in a zero magnetic environment, measuring the length of the magnetostrictive material rod and the cavity length of the Fabry–Perot cavity, and calculating the resonant frequency of the Fabry–Perot cavity as a preset reference resonant frequency; (2) placing the magnetic field measuring device in a magnetic field environment to be measured, forming a transmission spectrum according to the light signal detected by the photodetector, and then calculating the offset of the resonant frequency of the Fabry–Perot cavity compared to a preset reference resonant frequency according to the transmission spectrum, and then calculating the magnetic field size of the magnetic field environment according to the offset; Wherein, step (2) specifically includes: According to the optical power of the optical signal received by the photodetector, the transmittance of the optical signal received by the photodetector is calculated, and a transmission spectrum is formed; The resonant frequency of the Fabry–Perot cavity is obtained according to the transmission spectrum, and the offset of the resonant frequency of the Fabry–Perot cavity compared with the preset reference resonant frequency is calculated; The magnitude of the magnetic field in the magnetic field environment is calculated according to the following formula based on the offset: Where B is the magnitude of the magnetic field, L D is the length of the magnetostrictive material rod in a zero magnetic environment, α is the magnetostriction coefficient, L C is the length of the Fabry–Perot cavity in a zero magnetic environment, ω0 is the preset reference resonant frequency, and Δω is the offset.

8. The high-sensitivity magnetic field measurement method according to claim 7, characterized in that: In a zero magnetic environment, the ratio of the change in the cavity length of the Fabry–Perot cavity to the original cavity length can approach 1.

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